Optically readable storage media, such as music and software CD's and video DVD's, provide inexpensive ways to share and disseminate digital information, making such media the media of choice among both producers and consumers. This is clearly evident as CDs have nearly replaced cassette tapes and floppy disks in the music and software industries and DVDs have made significant inroads in replacing video cassette tapes in the home video industry. Because of the high demand for such optical media and because of the ease and low cost of reproduction, counterfeiting has become prevalent.
A variety of copy protection techniques and devices have been developed to limit the unauthorized copying of optical media. Among these techniques are analog Colorstripe Protection System (CPS), CGMS, Content Scrambling System (CSS) and Digital Copy Protection System (DCPS). Analog CPS (also known as Macrovision) provides a method for protecting videotapes as well as DVDs. The implementation of Analog CPS, however, may require the installation of circuitry in every player used to read the media. Typically, when a disk or tape is “Macrovision Protected,” the electronic circuit sends a colorburst signal to the composite video and s-video outputs of the player resulting in imperfect copies. The use of Macrovision may also adversely affect normal playback quality.
With CGMS, the media may contain information dictating whether or not the contents of the media can be copied. The device that is being used to copy the media must be equipped to recognize the CGMS signal and also must respect the signal in order to prevent copying. The Content Scrambling System (CSS) may provide an encryption technique that is designed to prevent direct, bit-to-bit copying. Each disk player that incorporates CSS is provided with one of four hundred keys that allow the player to read the data on the media, but prevents the copying of the keys needed to decrypt the data. However, the CSS algorithm has been broken and has been disseminated over the Internet, allowing unscrupulous copyists to produce copies of encrypted disks.
The Digital Copy Protection System (DCPS) provides a method whereby devices that are capable of copying digital media may only copy disks that are marked as copyable. Thus, the disk itself may be designated as uncopyable. However, for the system to be useful, the copying device must include the software that respects the “no copy” designation.
Each of these copy protection techniques, and others that may be available, may make it more difficult to copy material from optical media, and may deter the casual copyist. However, these techniques may be easily circumvented by the unscrupulous copyist who is intent on making digital copies of a disk.
In addition to directly copying content from optical media, producers and distributors of digital content are also adversely affected by unauthorized distribution of content over communications systems, such as the Internet. Known copy protection systems may not be capable of protecting a digital data file from being duplicated if it is intercepted by a copyist during transmission over these communication systems.